Hi folks, this is my first “big” MYOG project, and I thought, hey, why not put it to the forums for further insights.

I’m putting together my first UL solo shelter system and am tossing around ideas for an experimental bivy – rain cape – rain hat system. If I like the prototype after a few trips, I’ll re-construct it with better materials.

Sorry upfront for the length of this post; if I’m asking questions that have already been answered, feel free to point me in that direction. I’ve already found a number of relevant discussions, but keyword searches can only do so much.

I want to be multi-use, without going the route of a combo poncho/shelter. I am thinking about a bivy design where the bottom and top of the bivy would be separate, and assembled at night with Velcro tabs, or snaps, or zippers. The bottom could be used during the day as a rain cape, also covering my pack. I could strategically place Velcro etc to hold the cape together in a way that suits me. I experimented with sizing and it seems like this would cover me and my pack just as well as the cheap-o poncho I’ve been using. In bivy mode, I’d be able to open the bivy from either side, and also create ventilation as needed by opening some of the attachment points. I’d give the bottom nice high sides, and top fabric would overlap the bottom fabric a bit, to make up for it not being actually sewn together, to minimize big gaps and heat loss when I move around at night. I also want to make a large rain hat in the genre of “umbrella hat” (or maybe just get an umbrella hat). This hat could be attached at night to the head end of the bivy, coming up and over my head a bit, holding the bivy off my face and also providing a bit of protection against tarp walls if need be.

I still don’t know if this will be entirely practical for me. The reason I don’t want a raingear / shelter combo is that I’m in the Pacific Northwest so there’s often rain, and I want to hang out in camp in the rain with my shelter already set up, without bringing along an extra poncho. Those little cheap ponchos are only an ounce or two, but if I am scrounging around for ways to save a half-ounce here and there, it’s conceptually annoying to bring backup rain gear. But, having a bivy bottom / rain cape combo would mean that if it’s raining, I’ll still need to wait until bedtime to set up my sleep system, which will just wake me up more and make it harder for me to get to sleep—I’m already an insomniac.

Those of you with experience, does that sound like a potentially practical system, if I can get over the bedtime-setup issue? Would all the Velcro bits be so heavy that I’d do just as well to abandon the multi-use-as-rain-gear option and keep using my cheap 3.9 oz poncho as trail rain gear? (I’m an eternal grad student and don’t have cash to throw into too many things at once.)

Now on to materials:

For the top piece, it might be nice to have something more breathable and lighter than Tyvek (which I’m considering for the bottom) so I might as well get something that could be used in the final version. I’m considering M50 http://thru-hiker.com/materials/breathable.php and the 8D sold by TiGoat http://www.titaniumgoat.com/Fabric.html . The 8D is lower cost and about the same weight, I’m ordering some anyway for another project, and they say should be breathable enough. But I saw someone say that Momentum seems to hold their body heat in more than other similar-weight fabrics, which would be a bonus as I’m a cold sleeper. Any thoughts on that?

For the bottom / cape, I was thinking Tyvek, and then became tempted by polycryo, since it’s just temporary, and it’s so light, and others seem to be experimenting with it too for bivies and tarps; then again it’s heavy and might snag too easily for trail use. I have some 3x5 polycryo sheets laying around; does anyone have any experience with how waterproof it would be connecting them with the double-sided tape? Do you think Tyvek or polycryo would be OK for covering the footbox a bit, or is it not breathable enough and would cause moisture retention in the foot of my down bag?

If anyone has experience with affixing snaps, Velcro bits, tie-outs, etc to these materials, any words of advice? I haven’t done anything with Tyvek or Polycryo, and not much with “real” UL fabrics. I have strategies in mind but feel free to bestow any wisdom.

For the umbrella-hat, I was thinking of using wire to make the dome frame, covered with tyvek or polycryo for the dome. Or in place of wire, I could use a stiff foam. I made a “rough draft” using a couple pieces of pipe-insulation foam tubes I had lying around, shaped into a dome by the tension of string tied around the ends to bring them down into a square shape. For the real version, I’d cut the tubes into strips that I think would still be stiff enough to work, or use some other fairly stiff foam. Next, I’ll have to find some way of getting it to attach firmly to my head. Where I hike, it’s usually not terribly windy, so wind is not a huge design factor. I have big dreadlocks and wear them pulled together in a ball sort of on top of my head, and would love to be able to leave them up while wearing the hat, for ventilation comfort. So, any creative ideas are welcome.

You can probably tell by now that I care about practicality over looks— if I can visually entertain my hiking partners, all the better!

If anyone made it all the way through this post and still has energy to post your own ideas about it, thanks a million!

Thanks for your reply, Michael, and sorry for my delayed reply, not sure if you'll see this! A dry-bag closure bivy sounds fun. Just trying to visualize-- were you picturing that the bivy would be sort of like like an adjustable-length tube, fully-waterproof, and if used as rain gear, my pack and I would be effectually "inside" the tube? (with arm openings, etc) Or were you picturing it as a rain cape, and the dry bag closure would allow it to keep a full rectangular shape while worn as cape? Or something else? Thanks for any clarification-- I don't want to misunderstand what sounds like an interesting idea!

Similar idea to what you are thinking, been around for a fair while, though not well known. Its a bit heavy, no doubt you could lighten it up with other materials. WPB Cuben would probably work quite well for the torso and top off bottom sections, with something just waterproof for the bottom bottom bit (back of legs).